Method of sterilizing an orthopaedic implant

ABSTRACT

A pre-assembled orthopaedic implant adapted for improved gas sterilization. The implant includes a first component adapted for assembly with a second component such that a mating surface of the first component is in close proximity with a mating surface of the second component. At least one gas conduit associated with the mating surface of the first component facilitates a sterilizing gas to penetrate into and dissipate from the interface defined by the mating surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/914,551 filed on Aug. 9, 2004, which claims the benefit of U.S.Provisional Application No. 60/493,247, filed Aug. 7, 2003 and entitled“Modified Orthopaedic Implants for Improved Sterilization.” Thedisclosure of each application is incorporated by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

Appendix.

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to pre-assembled orthopaedicimplants adapted for gas sterilization.

2. Related Art

Orthopaedic implants, such as knee, hip or shoulder prostheses,occasionally include components that are shipped to the surgeon or otheruser in a pre-assembled condition. For example, a hip prosthesis mayinclude a bipolar component that includes a metal acetabular shellpre-assembled with a plastic liner. To lessen the chances ofpost-implantation failure, the shell and liner must fit together snugly,with a relatively tight interface between the two components.

Pre-assembled components, as well as other orthopaedic implantcomponents, may be sterilized prior to use to minimize the chances ofinfection. Orthopaedic components may be sterilized using a number ofdifferent techniques, including gas sterilization and gamma radiation.

In some circumstances, gas sterilization is a preferred technique forsterilizing orthopaedic components. Gas sterilization utilizes a gassuch as ethylene oxide (ETO) or vaporized hydrogen peroxide (VHP) toincapacitate bacterial or other disease causing agents. However, gassterilization May be ineffective in certain circumstances. For example,if during sterilization the gas is unable to contact all surfaces of theorthopaedic components, it may not effectively sterilize thosecomponents.

Typical pre-assembled orthopaedic components may not be suitable for gassterilization. Because of the relatively tight interface between thecomponents, the gas may not be able to penetrate between the componentsto sterilize all of the surfaces. Additionally, even if some of the gaspenetrates between the pre-assembled components, the gas may notnecessarily be able to effectively dissipate from in between the tightlyfitted pre-assembled components after sterilization is complete. Traceamounts of gas may remain in the implant, potentially having deleteriouseffects on the health of the individual who receives the implant.

Because typical pre-assembled orthopaedic implants may not be suitablefor gas sterilization, they have in the past been sterilized using theless preferable gamma irradiation technique. Gamma irradiation may causeoxidation of plastics, such as the polyethylene commonly used for theplastic liner of a pre-assembled orthopaedic component. Oxidation of thepolyethylene forming the plastic liner may weaken the component,increasing the chance that the implant will fail. Gamma irradiation mayalso be undesirable because it may neutralize the effects ofcross-linking in highly cross-linked plastic components, alsopotentially weakening the component.

SUMMARY OF THE INVENTION

Various embodiments of the present invention include a pre-assembledorthopaedic implant suitable for gas sterilization. In some embodiments,one or more gas conduits associated with one or more of the orthopaediccomponents facilitates the penetration and/or dispersion of asterilizing gas into and from the pre-assembled components, but do notaffect the mechanical integrity or overall performance of the implant.Embodiments of the present invention may include pre-assembled knee,hip, shoulder or other orthopaedic components.

In accordance with embodiments of the present invention, the gas conduitor conduits may be formed in several suitable shapes, sizes, locations,orientations or configurations. For example, in some embodiments the gasconduits are a plurality of channels inscribed onto a mating surface ofone or more of the orthopaedic components. In other embodiments, the gasconduits are one or more apertures passing through one or more of theorthopaedic components. Other embodiments may include any combination ofthe foregoing gas conduits, or other structures serving as suitable gasconduits.

Further features, aspects, and advantages of the present invention, aswell as the structure and operation of various embodiments of thepresent invention, are described in detail below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross-sectional view of a orthopaedic implantshown in a pre-assembled condition in accordance with a first embodimentof the present invention.

FIG. 2 shows a schematic view of the pre-assembled orthopaedic implantshown in FIG. 1 in a disassembled condition.

FIG. 3 shows a schematic cross-sectional view of an orthopaediccomponent in accordance with another embodiment of the presentinvention.

FIG. 4 shows a schematic view of an orthopaedic component in accordancewith another embodiment of the present invention.

FIG. 5 shows a schematic view of an orthopaedic hip implant inaccordance with another embodiment of the present invention, shown in adisassembled state.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to the accompanying drawings in which like reference numbersindicate like elements, FIG. 1 shows an orthopaedic implant 10 accordingto a first embodiment of the present invention. The implant 10 shown inFIG. 1 is adapted for implantation into the acetabulum of a hip suchthat the implant 10 can receive a prosthetic femoral head in a rotatingfashion (however, embodiments of the present invention also includeimplants that can interact with natural portions of the anatomy—such asnatural femoral heads). FIG. 5 shows (in a disassembled state) implant10 associated with a femoral head 30 and stem 32.

As shown in FIG. 1, orthopaedic implants 10 in accordance withembodiments of the present invention may include at least twoorthopaedic components 12 and 14. FIG. 1 shows the implant including twocomponents: an acetabular shell 12 and a liner 14. In the embodimentshown in FIG. 1, acetabular shell 12 is metal and liner 14 is a plastic,such as ultra high molecular weight polyethylene. However, shell 12 andliner 14 may be formed from any desirable material.

Implant 10 be assembled by press fitting liner 14 into an interiorcavity of acetabular shell 12 such that a mating surface 16 on the liner14 is in close proximity with a mating surface 18 of the acetabularshell 12, defining a mating surface interface 26. Liner 14 may besecured in shell 12 in any desirable, conventional, or non-conventionalmanner.

Implant 10 may be shipped with the liner 14 assembled in the shell 12and may be sterilized after assembly. If necessary or desired, thepre-assembled implant 10 may be later combined with other components tofinalize assembly of the implant prior to implantation. A retaining ring28 may secure the additional component to the pre-assembled implant.

Pre-assembled implant 10 may include one or more gas conduits 24. Gasconduits 24, as discussed above, may permit sterilization gasses such asETO or VHP to penetrate into the mating surface interface 26, betweenthe mating surfaces 16 and 18 of the shell 12 and liner 14. Gas conduits24 may also facilitate dispersion of the sterilization gas fromin-between the mating surfaces 16 and 18 of the components aftersterilization is complete. Gas conduits 24 may be formed as one or morechannels, one or more apertures, any combination of channels andapertures, or any other desired structure. The gas conduits 24 may beformed by machining, molding or any other conventional ornon-conventional technique.

FIG. 1 shows an aperture gas conduit 24 extending from an inner surfaceto the outer, mating surface 16 of the liner. FIG. 2 shows a pluralityof channel gas conduits 24 engraved in the mating surface 16 of theliner. In some embodiments, the liner may include both channels andapertures as gas conduits.

In still other embodiments, such as the embodiment shown in FIG. 4, theacetabular shell 12 may also include gas conduits 24, such as aperturesand channels. Gas conduits 24 associated with the acetabular shell 12may facilitate the penetration and subsequent dispersion of sterilizinggas in a similar manner to gas conduits 24 associated with the liner 14.

Gas conduits 24 may be associated with the shell 12, liner 14, or both,in any desired number, position or orientation to maximize thefacilitation of penetration and dispersion of sterilizing gas betweenthe mating surfaces 16 and 18 of the acetabular shell 12 and liner 14.For example, in the embodiment shown in FIGS. 1 and 2, the acetabularliner 14 includes three channels forming arcs on the surface of theliner 14 and one aperture at an apex of the liner 14. Alternatively, asthe embodiment in FIG. 3 shows, there are multiple apertures extendingthrough the acetabular liner 14. In the alternate embodiment shown inFIG. 4, multiple channels and multiple apertures are associated with theacetabular shell 14.

As those skilled in the art will appreciate, the particular embodimentof this invention described above and illustrated in the figures isprovided for explaining the invention, and various alterations may bemade in the structure and materials of the illustrated embodimentwithout departing from the spirit and scope of the invention asdescribed above. For example, orthopaedic implants in accordance withthe present invention are not limited to acetabular shells and liners.Pre-assembled implants for use with knees, shoulders or other joints ofthe anatomy may also include gas conduits for improved sterilization inaccordance with the embodiments of the present invention.

1. A method of sterilizing an orthopaedic implant comprising: a.assembling an orthopaedic implant comprising: i. a first orthopaediccomponent, the first orthopaedic component comprising a firstorthopaedic component mating surface; ii. a second orthopaediccomponent, the second orthopaedic component having a second orthopaediccomponent mating surface, the first orthopaedic component beingassembled to the second orthopaedic component such that the firstcomponent mating surface confronts the second component mating surfaceto define a mating surface interface; and iii. at least one gas conduitassociated with the first orthopaedic component mating surface; and b.subjecting the assembled orthopaedic implant to a gas sterilizationprocess such that the at least one gas conduit facilitates asterilization gas to substantially penetrate the mating surfaceinterface.
 2. The method of sterilizing an orthopaedic implant of claim1, wherein subjecting the assembled orthopaedic implant to a gassterilization process comprises subjecting the assembled orthopaedicimplant to an ethylene oxide gas sterilization process.
 3. The method ofsterilizing an orthopaedic implant of claim 1, wherein subjecting theassembled orthopaedic implant to a gas sterilization process comprisessubjecting the assembled orthopaedic implant a vaporized hydrogenperoxide gas sterilization process.
 4. A method of sterilizing anorthopaedic implant comprising the steps of: a. providing a firstorthopaedic component, the first orthopaedic component having a firstorthopaedic component mating surface; b. providing a second orthopaediccomponent, the second orthopaedic component having a second orthopaediccomponent mating surface; c. associating at least one gas conduit withat least one of the first orthopaedic component mating surface and thesecond orthopaedic component mating surface; d. assembling the secondorthopaedic component to the first orthopaedic component such that thefirst component mating surface confronts the second component matingsurface to define a mating surface interface; and e. subjecting theassembly to a gas sterilization process such that the at least one gasconduit facilitates a sterilization gas to substantially penetrate themating surface interface.
 5. The method of sterilizing an orthopaedicimplant of claim 4, wherein the step of subjecting the assembly to a gassterilization process comprises subjecting the assembly to an ethyleneoxide gas sterilization process.
 6. The method of sterilizing anorthopaedic implant of claim 4, wherein the step of subjecting theassembly to a gas sterilization process comprises subjecting theassembly to a vaporized hydrogen peroxide gas sterilization process. 7.The method of sterilizing an orthopaedic implant of claim 4, wherein theat least one gas conduit is associated with the first orthopaediccomponent mating surface.
 8. The method of sterilizing an orthopaedicimplant of claim 4, wherein the at least one gas conduit is associatedwith the second orthopaedic component mating surface.
 9. The method ofsterilizing an orthopaedic implant of claim 4, wherein the at least onegas conduit is associated with both the first orthopaedic componentmating surface and the second orthopaedic component mating surface. 10.The method of sterilizing an orthopaedic implant of claim 4, wherein thestep of assembling the second orthopaedic component to the firstorthopaedic component comprises press fitting the second orthopaediccomponent into the first orthopaedic component.
 11. The method ofsterilizing an orthopaedic implant of claim 4, further comprising thesteps of: a. providing a stem; b. assembling a femoral head to the stem;and c. assembling the femoral head to the first orthopaedic component orthe second orthopaedic component.
 12. The method of sterilizing anorthopaedic implant of claim 4, further comprising the step ofassembling a retaining ring to the shell.
 13. A method of sterilizing anorthopaedic implant comprising the steps of: a. providing a liner, theliner having a liner mating surface and at least one gas conduit; b.providing a shell, the shell having a shell mating surface; c.assembling the liner to the shell such that the liner mating surfaceconfronts the shell mating surface to define a mating surface interface;and d. subjecting the assembled shell and liner to a gas sterilizationprocess such that the at least one gas conduit facilitates asterilization gas to substantially penetrate the mating surfaceinterface.
 14. The method of sterilizing an orthopaedic implant of claim13, wherein the step of subjecting the assembly to a gas sterilizationprocess comprises subjecting the assembly to an ethylene oxide gassterilization process.
 15. The method of sterilizing an orthopaedicimplant of claim 13, wherein the step of subjecting the assembly to agas sterilization process comprises subjecting the assembly to avaporized hydrogen peroxide gas sterilization process.
 16. The method ofsterilizing an orthopaedic implant of claim 13, wherein the step ofassembling the liner to the shell comprises press fitting the liner intothe shell.
 17. The method of sterilizing an orthopaedic implant of claim13, further comprising the step of assembling a femoral head to theliner.
 18. The method of sterilizing an orthopaedic implant of claim 13,further comprising the steps of: a. providing a stein; b. assembling afemoral head to the stem; and c. assembling the femoral head to theliner.
 19. The method of sterilizing an orthopaedic implant of claim 13,further comprising the step of securing the femoral head.
 20. The methodof sterilizing an orthopaedic implant of claim 13, further comprisingthe step of assembling a retaining ring to the shell.